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United States Department of Agriculture

Agricultural Research Service


Location: Wheat Genetics, Quality Physiology and Disease Research

2008 Annual Report

1a. Objectives (from AD-416)
Investigate the genetic mechanisms by which the plant hormones abscisic acid (ABA) and gibberellin (GA) control pre-harvest sprouting stand establishment, and drought and cold tolerance in wheat and model organisms. Develop and utilize molecular markers for the western region wheat and barley breeding programs for resistance to biotic and abiotic stress, and end-use quality. Develop wheat cultivars with durable resistance to stripe rust, soilborne diseases, cold and drought, and improved end-use quality for Western Region cropping systems using wheat germplasm resources from the USDA-ARS National Small Grains Germplasm Collection (NSGC) and other national and international sources.

1b. Approach (from AD-416)
Determine whether ABA sensitivity controls grain dormancy and tolerance to preharvest sprouting. Determine whether degree of drought tolerance and cold tolerance tend to correlate with each other and depend upon ABA sensitivity. Determine how GA signaling controls seed dormancy and plant height. Identify and use new and existing molecular markers linked to genes for biotic stress resistance, specifically for stripe rust resistance. Identify and use new molecular markers for genes linked to abiotic and end-user quality. Establish and use high-throughput molecular marker analysis systems to track the segregation of important genes in wheat and barley breeding programs. Characterize core wheat germplasm sets for use in identifying haplotypes important in Western Regional germplasm adaptation. Use molecular markers to link genotypes to phenotypes while maintaining critical haplotypes for enhancement, disease resistance and end-use quality in Western Region wheat breeding programs. Identify new sources of genes giving superior end-use quality, disease resistance, and resistance to cold and drought. Pharmacological agents that enhance or inhibit phospholipase enzyme activity will be used in whole-plant assays to assess their impact on cold acclimation and freezing tolerance; concomitant microarray analysis will be used to define the genes involved.

3. Progress Report
OBJECTIVE 1: Wheat mutants, hypersensitive to abscisic acid (ABA) were characterized using ABA dose-response germination experiments, stomatal closure assays, and carbon isotope discrimination. One mutant showed a reproducible stomatal closure in response to ABA application resulting in measured increase in transpiration efficiency, indicating that it may be more drought tolerant. Drought tolerance experiments were established in the field in 2008. The role of the plant hormone, Giberellin in seed germination and plant height was investigated. The DELLA protein, RGA was shown to be controlled by protein-protein interaction with GA receptor GID1 in Arabidopsis. GID1 can deactivate germination-specific DELLA protein RGL2. The effect of GID1 on seed dormancy is similar to the effect of after-ripening suggesting the processes may share underlying mechanisms. OBJECTIVE 2: 105,797 molecular marker datapoints have been provided to wheat and barley researchers as follows: 6,659 (CA), 32,546 (ID), 9,642 (OR), 10,726 (MT), and 46,528 (WA). 58% of those datapoints were linked to disease resistance genes, 27% to quality traits and 15% to agronomic traits. 55% of the markers linked to disease resistance were for resistance to leaf, stripe and stem rust. The genotyping lab assisted in identification and validation of new markers for seed coat color, eyespot resistance, and new rust genes, Lr57/Yr40. 475 genotypes have been collected from wheat breeders in MT, OR, CA, ID, and WA, single plant DNA was isolated from all lines, and over 6,000 datapoints have been analyzed. Individual genotype haplotypes have been identified, critical in varietal purity screens (11,290 datapoints) and in Plant Varietal Protection. OBJECTIVE 3: The repeatability of the small-scale solvent retention capacity test for grain end use quality was assayed with the result that two of the four SRC tests are reliable to use in early generations in breeding programs. Over 18,000 Triticum accessions from the National Small Grains germplasm collection that had at least moderate resistance to stripe rust were clustered according to geographic, morphological and agronomic characteristics recorded in the GRIN database. A subset of 500 of those accessions was designated as a core collection of stripe rust resistant germplasm. Wheat breeding lines from regional extension variety trials and from the Western Regional winter wheat nurseries were assayed for tolerance to freezing in artificial freezing tests conducted at the Washington State University wheat plant growth center. Resistance to Fusarium pseudograminearum was assayed using greenhouse and terrace bed screening systems in breeding lines and in a spring wheat population segregating for resistance in order to identify quantitative trait loci associated with that trait. Eight experimental soft wheat breeding lines with competitive agronomic traits, resistance to stripe rust and strawbreaker foot rot, and excellent soft wheat end use quality were entered into either the Western Regional soft winter wheat trial or the Washington State soft wheat variety trials. This research is relevant to NP301, Component 3, Problem 3C and NP306, Comp. 1

4. Accomplishments
1. This project started in April 2008. All accomplishments are listed on the termed project 5348-21220-003-00D.

Review Publications
Sherman, J.D., Souza, E.J., See, D.R., Talbert, L.E. 2008. Microsatellite markers for kernel color genes in wheat. Crop Science. 48:1419-1424.

Finkelstein, R., Reeves, W., Ariizumi, T., Steber, C.M. 2008. Molecular aspects of seed dormancy. Annu. Rev. Plant Biol. 59:387-415.

Walker, C., Garland Campbell, K.A., Carter, B., Kidwell, K. 2008. Using the solvent retention capacity test when breeding wheat for diverse production environments. Crop Sci. 48: 495-506.

Last Modified: 10/19/2017
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